Abstract: In a previous study, we used transmission electron microscopy and electron energy-loss (EEL) spectroscopy to investigate dehydrogenation of AlH3 particles. In the present study, we systematically examine differences in the chemical bonding states of Al-containing compounds (including AlH3) by comparing their Al-L2,3 EEL spectra. The spectral chemical shift and the fine peak structure of the spectra were consistent with the degree of covalent bonding of Al. This finding will be useful for future nanoscale analysis of AlH3 dehydrogenation toward the cell.

Abstract: New apparatus and a new process for the sputter deposition of modified barium titanate thin-films were developed. Films were deposited at temperatures up to 900 °C from a Ba0.96Ca0.04Ti0.82Zr0.18O3 (BCZTO) target directly onto Si, Ni and Pt surfaces and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Film texture and crystallinity were found to depend on both deposition temperature and substrate: above 600 °C, the as-deposited films consisted of well-facetted crystallites with the cubic perovskite structure. A strongly textured Pt (111) underlayer enhanced the (001) orientation of BCZTO films deposited at 900 °C, 10 mtorr pressure and 10% oxygen in argon. Similar films deposited onto a Pt (111) textured film at 700 °C and directly onto (100) Si wafers showed relatively larger (011) and diminished intensity (00ℓ) diffraction peaks. Sputter ambients containing oxygen caused the Ni underlayers to oxidize even at 700 °C: Raising the process temperature produced more diffraction peaks of NiO with increased intensities. Thin-film capacitors were fabricated using ~500 nm thick BCZTO dielectrics and both Pt and Ni top and bottom electrodes. Small signal capacitance measurements were carried out to determine capacitance and parallel resistance at low frequencies and from these data, the relative permittivity (er) and resistivity (r) of the dielectric films were calculated; values ranged from ~50 to >2,000, and from ~104 to ~1010 Ω∙cm, respectively.

Abstract: A standard X-observe NMR probe was equipped with a z-gradient coil to enable high-sensitivity pulsed field gradient NMR diffusion studies of Li+ and Cs+ cations of aqueous salt solutions in a high-porosity mesocellular silica foam (MCF) and of CO2 adsorbed in metal-organic frameworks (MOF). The coil design and the necessary probe modifications, which yield pulsed field gradients of up to ±16.2Tm−1, are introduced. The system was calibrated at 2H resonance frequency and successfully applied for diffusion studies at 7Li, 23Na, 13C and 133Cs frequencies. Significant reductions of the diffusivities of the cations in LiClac and CsClac solution introduced into MCFs are observed. By comparison of the diffusion behavior with the bulk solutions, a tortuosity of the silica foam of 4.5 ± 0.6 was derived. Single component self-diffusion of CO2 and CH4 (measured by 1H NMR) as well as self-diffusion of the individual components in CO2/CH4 mixtures was studied in the MOF CuBTC. The experimental results confirm high mobilities of the adsorbed gases and trends for diffusion separation factors predicted by MD simulations.

Abstract: A rapid and simple immuno-chromatographic assay was developed to detect aflatoxin B1 (AFB1). The assay was based on a modified competitive binding format using colloidal gold and polyclonal antibody (Pab) conjugates. The anti-AFB1 Pab was immobilized to a defined detection zone on a porous nitrocellulose membrane and colloidal gold particles were conjugated to AFB1-BSA which served as a detection reagent. The AFB1-containing sample was added to the membrane and allowed to move with AFB1-BSA-coated particles dried on the conjugation pad. The mixture was then passed along the porous membrane by capillary action past the Pab in the detection zone, which captured AFB1 or AFB1-BSA. AFB1 in the sample inhibits binding of AFB1-BSA conjugated gold particles to the Pab and prevents formation of a red color dot. In the absence of AFB1, AFB1-BSA conjugated gold particles bound to the Pab, give a red color within this detection zone. With this method, 10 μg/mL of AFB1 was detected in less than 10 min. The developed AFB1 assay also showed no cross reaction to Ochratoxin A (OTA).

Abstract: Simple thin-film capacitor stacks were fabricated from sputter-deposited doped barium titanate dielectric films with sputtered Pt and/or Ni electrodes and characterized electrically. Here, we report small signal, low frequency capacitance and parallel resistance data measured as a function of applied DC bias, polarization versus applied electric field strength and DC load/unload experiments. These capacitors exhibited significant leakage (in the range 8–210 μA/cm2) and dielectric loss. Measured breakdown strength for the sputtered doped barium titanate films was in the range 200 kV/cm −2 MV/cm. For all devices tested, we observed clear evidence for dielectric saturation at applied electric field strengths above 100 kV/cm: saturated polarization was in the range 8–15 μC/cm2. When cycled under DC conditions, the maximum energy density measured for any of the capacitors tested here was ~4.7 × 10−2 W-h/liter based on the volume of the dielectric material only. This corresponds to a specific energy of ~8 × 10−3 W-h/kg, again calculated on a dielectric-only basis. These results are compared to those reported by other authors and a simple theoretical treatment provided that quantifies the maximum energy that can be stored in these and similar devices as a function of dielectric strength and saturation polarization. Finally, a predictive model is developed to provide guidance on how to tailor the relative permittivities of high-k dielectrics in order to optimize their energy storage capacities.

Abstract: Transparent conducting oxides (TCOs) are electrical conductive materials with comparably low absorption of electromagnetic waves within the visible region of the spectrum. They are usually prepared with thin film technologies and used in opto-electrical apparatus such as solar cells, displays, opto-electrical interfaces and circuitries. Here, based on a modern database-system, aspects of up-to-date material selections and applications for transparent conducting oxides are sketched, and references for detailed information are given. As n-type TCOs are of special importance for thin film solar cell production, indium-tin oxide (ITO) and the reasonably priced aluminum-doped zinc oxide (ZnO:Al), are discussed with view on preparation, characterization and special occurrences. For completion, the recently frequently mentioned typical p-type delafossite TCOs are described as well, providing a variety of references, as a detailed discussion is not reasonable within an overview publication.

Abstract: The purpose of this study was to determine the effect of the covalent incorporation of hyaluronic acid (HA) into conventional hydrogel and hydrogels containing silicone as models for contact lens materials on the uptake and release of the fluoroquinolone antibiotic ciprofloxacin and the anti-inflammatory steroid dexamethasone phosphate. A 3 mg/mL ciprofloxacin solution (0.3% w/v) and a 1 mg/mL dexamethasone phosphate solution (0.1%) was prepared in borate buffered saline. Three hydrogel material samples (pHEMA; pHEMA TRIS; DMAA TRIS) were prepared with and without the covalent incorporation of HA of molecular weight (MW) 35 or 132 kDa. Hydrogel discs were punched from a sheet of material with a uniform diameter of 5 mm. Uptake kinetics were evaluated at room temperature by soaking the discs for 24 h. Release kinetics were evaluated by placing the drug-loaded discs in saline at 34 °C in a shaking water bath. At various time points over 6–7 days, aliquots of the release medium were assayed for drug amounts. The majority of the materials tested released sufficient drug to be clinically relevant in an ophthalmic application, reaching desired concentrations for antibiotic or anti-inflammatory activity in solution. Overall, the silicone-based hydrogels (pHEMA TRIS and DMAA TRIS), released lower amounts of drug than the conventional pHEMA material (p < 0.001). Materials with HA MW132 released more ciprofloxacin compared to materials with HA MW35 and lenses without HA (p < 0.02). Some HA-based materials were still releasing the drug after 6 days.

Abstract: When a porous material is inserted into a uniform magnetic field, spatially varying fields typically arise inside the pore space due to susceptibility contrast between the solid matrix and the surrounding fluid. As a result, direct measurement of the field variation may provide a unique opportunity to characterize the pore geometry. The sensitivity of nuclear magnetic resonance (NMR) to inhomogeneous field variations through their dephasing effects on diffusing spins is unique and powerful. Recent theoretical and experimental research sheds new light on how to utilize susceptibility-induced internal field gradients to quantitatively probe the microstructure of porous materials. This article reviews ongoing developments based on the stimulated echo-pulse sequence to extend the characterization of porous media using both spatially resolved and unresolved susceptibility-induced internal gradients that operate on a diffusing-spin ensemble.

Abstract: With the advent of mesoporous zeolites, the exploration of their transport properties has become a task of primary importance for the auspicious application of such materials in separation technology and heterogeneous catalysis. After reviewing the potential of the pulsed field gradient method of NMR (PFG NMR) for this purpose in general, in a case study using a specially prepared mesoporous zeolite NaCaA as a host system and propane as a guest molecule, examples of the attainable information are provided.

Abstract: Because of the small particle size, orientation-dependent diffusion measurements in microporous materials remains a challenging task. We highlight here the potential of micro-imaging by interference microscopy in a case study with MFI-type crystals in which, although with different accuracies, transient concentration profiles in all three directions can be observed. The measurements, which were performed with “rounded-boat” shaped crystals, reproduce the evolution patterns of the guest profiles recorded in previous studies with the more common “coffin-shaped” MFI crystals. The uptake and release patterns through the four principal faces (which in the coffin-shaped crystals extend in the longitudinal direction) are essentially coincident and there is no perceptible mass transfer in the direction of the long axis. The surface resistances of the four crystal faces through which mass transfer occurs are relatively small and have only a minor effect on the mass transfer rate. As a result of the pore structure, diffusion in the crystallographic c direction (which corresponds to the direction of the long axis) is expected to be much slower than in the transverse directions. This could explain the very low rate of mass transfer observed in the direction of the long axis, but it is also possible that the small end faces of the crystal may have high surface resistance. It is not possible to distinguish unequivocally between these two possibilities. All guest molecules studied (methyl-butane, benzene and 4-methyl-2-pentyne) show the same orientation dependence of mass transfer. The long 4-methyl-2-pentyne molecules would be expected to propagate at very different rates through the straight and sinusoidal channels. The coinciding patterns for uptake through the mutually perpendicular crystal faces therefore provide clear evidence that both the coffin shaped crystals and the rounded-boat-shaped crystals considered in this study, must be intergrowths rather than pure single crystals.